The invention relates to an apparatus for inspecting a pipeline for leaks particularly an apparatus is one that can be carried through the pipeline with the stream of matter flowing through that pipeline. The apparatus includes equipment for detecting, amplifying, selecting and recording acoustic signals received from leaks or external coded sources of vibration.
The outward appearance of such an apparatus may resemble a cylindrical housing with a smaller diameter than the internal diameter of the pipeline, and equipped with flanges which do not touch the inner wall of the pipeline and wheels rolling along that inner wall.
A small leak in a pipeline, in particular in a pipeline for liquids such as oil or oil products, causes a hissing sound, which is readily perceptible in the pipeline in the proximity of that leak. For this purpose the apparatus is equipped with a microphone or hydrophone attached to the outside of the cylindrical housing. The sound produced includes both audible and ultrasonic vibrations. As it travels through the pipeline the apparatus detects a rise in sound intensity when approaching a leak and a fall when the leak has been passed. The recitified signal is peak-shaped and the peak is recorded as a function of time it is possible to determine the position of the leak with the aid of the flow schedule of the pipeline. It is sufficient to print the time on the record sheet when a leak is being passed. Favorable results are obtained when the apparatus is designed for the detection and processing of vibrations in the range of 20-40 kHz.